1. Field of the Invention:
The present invention pertains to a process and apparatus for high speed texturizing of thermoplastic yarns and, more particular, to such process and apparatus for simultaneously texturizing a plurality of thermoplastic yarns and to the product produced thereby.
2. Discussion of the Prior Art:
In the past a great number of processes have been utilized to produce springy texturized yarn with such prior art processes being specifically described in the above mentioned patent application Ser. No. 56,880, now U.S. Pat. No. 3,703,754, the specification of which is incorporated herein by reference. In order to more fully appreciate the present invention, however, prior art texturizing processes will be briefly described hereinafter.
The false twist process, which is an example of a mechanical texturizing process, is utilized for texturizing by subjecting a yarn to an excess twist that is thermally fixed and then continuously untwisting the yarn. Another mechanical texturizing process is stuffing wherein a heated yarn is compressed in a stuffing box in which it remains for varying lengths of time. The mechanical texturizing processes as described above have the disadvantage of permitting only relatively low rates of production and, therefore, have not been as commercially feasible as is desirable.
U.S. Pat. No. 3,373,470 describes a texturizing process that permits high rates of production on the order of 1,000 meters per minute or greater by compacting and compressing yarns in a limited space by means of a hot fluid under pressure. One portion of the fluid is permitted to escape laterally while the remaining portion of the fluid effects the advance of the packed yarn within the limited space. The apparatus utilized to effect the process of U.S. Pat. No. 3,373,470 basically includes a suction nozzle having a yarn passage extending therethrough and a pipe for delivering the hot fluid. A tubular chamber communicates with a nozzle receiving the hot fluid and the yarn, and the tubular chamber has gaps in its lateral wall to permit escape of the fluid. The process of Pat. No. 3,373,470 is particularly effective in texturizing of high tex yarns, such as carpet yarns, and medium tex yarns, and this process is presently commercially utilized for texturizing yarns above 500 dtex.
The process and apparatus of U.S. Pat. No. 3,373,470 cannot be easily utilized to texturize fine yarns, that is yarns below 100 dtex, in that the dimensions of the apparatus must be reduced to the size of the yarn to be treated. Accordingly, in order to utilize this process for fine yarns the apparatus must be miniaturized which, of course, involves the disadvantages of precise machining and design of the gaps or piercing of the lateral escape holes for the fluid. In many cases the diameter of such escape holes must be on the order of 0.1mm. The provision of such small holes without leaving burrs inside the tubular chamber is an extremely difficult operation and from an economic standpoint is improper.
The process of U.S. Pat. No. 3,373,470 has been utilized to assemble and texturize simultaneously two or more 500 dtex yarns by feeding several filament lengths together to the input of the texturizing device. At the output of the device a pack formed of a curling or crimped yarn, whose number of filaments is the sum of the number of filaments introduced into the device, is collected, the pack being normally collected in a skip or can. When the treated yarns are on the order of 500 dtex, it is possible to separate the different yarns in the pack without great difficulty since the yarns have a relatively high tex and are, accordingly, relatively heavy. Of course, the yarns have a tendency to stick or cling together, however, in the case of high titre yarns, when the yarns are extracted or removed from the skip or can the yarns separate due to the weight of the pack. In contradistinction; however, when fine yarns are treated, such fine yarns have a tendency to cling together even if they are not texturized; and, thus when they are texturized, the interengagement due to the kinks is stronger and is capable of resisting the effect of the weight of the pack. Accordingly, separation of the yarns is extremely difficult; and, of course, the degree of difficulty increases with the decrease in titre or increase in fineness of the texturized yarns. Furthermore, in certain applications the pack of texturized yarns after collection in a skip or can is subjected to additional treatments such as passage through a dye bath. During such additional treatments or operations the pack is subjected to movement which exposes the pack to deformation that could cause the pack to loose cohesion and its original configuration, such as crushing for example. If such deformation occurs, the difficulty in separating the yarns from the pack is greatly increased since the yarns are meshed and cling to each other with increased tenacity.
To increase consistency and firmness of packs produced by the above processes an auxiliary yarn has been introduced into the texturizing device along with the yarn to be treated. The auxiliary yarn is fed at a slower speed than the yarn to be treated and constitutes a core imparting firmness to the pack. The use of such an auxiliary yarn has the disadvantage of requiring the delivery of a further element to the texturizing device, which element must then be removed from the pack by chemical, physical or mechanical means. Another manner in which it has been attempted to increase consistency and firmness of the pack is to incorporate a binder in the yarn substance; however, this solution has the disadvantage of effectively providing a compromise between the firmness of the produced pack to facilitate further operations and the facility of extracting or separating the yarn from the pack for winding. Furthermore, the binder must be such as not to have a chemical or physical effect on the yarn such as bonding the strands since such an effect produces a yarn having irregular bulk or cross section.
Another problem in the separation of texturized yarns is that in the past separation was possible only at low speeds, and, thus, the entire process was slowed thereby. Of course, high speeds in the production of texturized yarns are greatly desirable.